The present invention relates to light displays and, more particularly, to a light guide which produces a thin line of light of a desired length. The line of light is particularly suitable for use in highlighting components in an automotive dashboard or console, or in providing a visual display in consumer or industrial electronic equipment.
A light guide is a device through which light travels. Rays of light travelling in the light guide can change direction according to the principle of total internal reflection. When a ray of light travels through one medium, such as the light guide, and strikes the boundary of a second medium with lower refractive index, such as air, total internal reflection can result if the angle of incidence is sufficiently oblique. The required angle is known as the critical angle. Moreover, the incident light ray will be reflected internally at an angle equal to the angle of incidence. The boundary of the light guide then becomes a reflecting surface. Rays from a point light source can thus be directed in a predetermined direction if the position of the light source and the geometry of the reflecting surface is known.
Light display devices which employ point sources and light guides have been used, for example, for automobile stoplights, where it is desirable to minimize the thickness of the device. Such devices may use a number of point light sources which are viewed from behind a diffuse lens which provides a display with a relatively uniform intensity. Alternatively, a continuous line of light can be produced from a laser diode module, light emitting diode module, high pressure neon tubular discharge lamp, or fiber optic array. Examples of such devices can be found in U.S. Pat. Nos. 5,165,772 and 4,929,866.
Light display devices are also used in illuminated dials, where indicia are inscribed on a display surface of a light guide. The indicia are visible due to backlighting provided by the light guide, as disclosed in U.S. Pat. No. 2,561,885. A light display device has also been used to provide an illuminated panel for examination of objects placed thereon, as shown in U.S. Pat. No. 5,136,480. Such an illuminated panel is useful in medical applications such as phototherapy.
In contrast, the present invention provides a long, thin illuminated line of light which is particularly suitable for use in highlighting components in an automotive dashboard or console, consumer product, industrial control panel, or the like. For example, a cup holder, gearshift console or other automotive accessory can be highlighted for easier viewing and location by the driver or passengers. The present invention can also be used, for instance, in producing functional or aesthetic visual displays for consumer electronic equipment. For example, one or more lines of light can be used as volume intensity or frequency spectrum displays in a home stereo system. Various other applications are possible.